Brake Disk Punching Confusion

[2_DONE_THE_TON]

wow sonic those discs look rad..... :

what drill diameter did you use for these?
i see no chamfering on these...ill stick to your opinion xb...
thsnks guys for the input!

btw sonic

what kind of paint setup did you use for your mattee back fork and disk color?what kind of primer did you use?
it looks great-...

 

[SONICJK]

wow sonic those discs look rad.....

what drill diameter did you use for these?
i see no chamfering on these...ill stick to your opinion xb...
thsnks guys for the input!

btw sonic

what kind of paint setup did you use for your mattee back fork and disk color?what kind of primer did you use?
it looks great-...

Those holes are 1/4" and they are not chamfered.
And all the black is powdercoat

 

[SONICJK]

and do not chamfer the holes one of the things that the unchamfered holes are beneficial for is helping to clean the pad surface while in use
nothing wrong with larger holes either as long as there aren't too many closely spaced

chamfered holes will just ruin your discs,they will get scored up over time .......unless you don't ride

The problem with large holes is that you can actually decreasing the surface area of the rotor, which makes the drilling counter productive.

 

[xb33bsa]

Those holes are 1/4" and they are not chamfered.
And all the black is powdercoat

they look sweet nice job 1
agreed too many large holes counterproductive

 

[2_DONE_THE_TON]

The problem with large holes is that you can actually decreasing the surface area of the rotor, which makes the drilling counter productive.

wow seems like you hand drilled those holes...
how did you go about?
marking-pre-drilling with a smaller drill (which size?)?
how many times did you pre drill?
did you use drill oil?

 

[SONICJK]

It's not tough.
I use a drill press at 320 Rpms. Use cutting oil or dish soap.
Use a cobalt bit (5 bucks at your local big box store)
I do not pre drill, I use a center punch to mark center on the holes and then drill with steady pressure.
A cobalt bit will do several hundred holes before sharpening

 

[2_DONE_THE_TON]

hey guys!

i successfully drilled my disk..they look rad.

It's not tough.
I use a drill press at 320 Rpms. Use cutting oil or dish soap.
Use a cobalt bit (5 bucks at your local big box store)
I do not pre drill, I use a center punch to mark center on the holes and then drill with steady pressure.
A cobalt bit will do several hundred holes before sharpening

i dont wanna chamfer these holes...how do you get rid of the sharp edges of the holes?i dont want to sand it or use any other abrasive material that will break the surface of the disk.

 

[D4N63R]

when we need to clean up rotors on the race bikes we glass bead blast them. makes them good as new, if you have access to a blasting cabinet.

 

[xb33bsa]

glass beading won't remove burs but yeah a good way to get a fresh surface to bed-in new pads
you are going to need to use an abrasive a new fresh large flat oilstone carefully used can do the trick
scuff up the surface of the disc with cross-hatch scratches as you spin the wheel
another way to do it without creating a large chamfer is use a new 12mm or so spherical ball carbide bur that is designed for a die grinder just use it with a hand held chuck and kiss each hole hahahahahaaha

 

[2_DONE_THE_TON]

when we need to clean up rotors on the race bikes we glass bead blast them. makes them good as new, if you have access to a blasting cabinet.

i have no access to one.

glass beading won't remove burs but yeah a good way to get a fresh surface to bed-in new pads
you are going to need to use an abrasive a new fresh large flat oilstone carefully used can do the trick
scuff up the surface of the disc with cross-hatch scratches as you spin the wheel
another way to do it without creating a large chamfer is use a new 12mm or so spherical ball carbide bur that is designed for a die grinder just use it with a hand held chuck and kiss each hole hahahahahaaha

wow seems like the work has JUST begun

thought about using sanding paper...like 120 or higher and carefully handgrind over the edges.

still waiting for your answer SONIC!!

 

[o1marc]

Not chamfering the holes can leave sharp edges that could be prone to stress cracking. Sharp edges do aide in constantly scrapping the pad surface clean, but more so than necessary and causes premature were out the pads.

 

[xb33bsa]

Not chamfering the holes can leave sharp edges that could be prone to stress cracking. Sharp edges do aide in constantly scrapping the pad surface clean, but more so than necessary and causes premature were out the pads.

stress cracking ?because the edge is not chamfered? that is just hilarious ;D
a cast iron disc with TOO MANY holes and then OVERHEATED may indeed, crack but we are not talking about cast iron
premature wear? not if the edge is free of a bur that hangs into the pad travel
IDEALLY the disc is ground after holes are created that is the way the oem and aftermaket discs are done many of them actually have punched holes
nobody that knows wtf they are doing chamfers the holes all that does is CREATE excess scoring and wear on the disc

 

[SONICJK]

I put 320 grit paper on and orbital and lightly sand the surface of the rotor.
Gets the burs off without doing much to the surface.

 

[2_DONE_THE_TON]

I put 320 grit paper on and orbital and lightly sand the surface of the rotor.
Gets the burs off without doing much to the surface.

thanks sonic for your help!

i used a chamfering drill and kissed it for 2 milliseconds so the burs are gone and there is no real chamfering,the burs got literally peeled off.
then i took an 80 grit paper worked on the holes,then a 120 paper....and they look good and feel plain.

another question SONIC:

are they even safe to ride ?

 

[SONICJK]

thanks sonic for your help!

i used a chamfering drill and kissed it for 2 milliseconds so the burs are gone and there is no real chamfering,the burs got literally peeled off.
then i took an 80 grit paper worked on the holes,then a 120 paper....and they look good and feel plain.

another question SONIC:

are they even safe to ride ?

That works just fine.

Safe to ride? How so?

 

[2_DONE_THE_TON]

That works just fine.

Safe to ride? How so?

i was just wondering,googled the procedure during the process of drilling these holes and everyone in the web was like "OH NO DONT DO THAT,,,,THE DISKS WILL EXPLODE!!!"

you seem to ride pretty safely with yours ?i jsut want to know before these drilled suckers will fall apart in front of me ;-)

 

[SONICJK]

Oh haha you're 100% fine.
Watch for cracking around the holes but thousands if not millions of vehicles run drilled /slotted rotors every day with no issue.

 

[jpmobius]

Hey Ryan,

Caught your thread a bit late. Just for your peace of mind, here is an rd350 rotor. It has at least 20,000 miles of very serious use. It has about as much material removed as I would recommend, but it is still flat enough to have no observable problems either from inspection or riding. The chamfering issue is debatable, but certainly doing more than de-burring is pointless. You may as well drill larger holes and at least take off the weight. This one has never been surfaced except for deglazing with sandpaper. I spin my discs when I do that, but the stainless is so hard, you could likely do it with a DA on the bench just as well. The holes here are larger than the thickness of the rotor. This brake does not suffer any noticeable reduction in performance over the stock one, but is reliable, safe, and noticeably lighter. Nice work, and good comments all.

edit: Just noticed your disc is different. The disc in my pic is 7mm thick from a 1973 RD350 from the US. Your disc should be bulletproof!

 

[cxman]

the engineering calcs for rotor drilling

The formula is like this:
t: Disc thickness
d: Hole diameter

If d<2t the surface area will increase
If d=2t the surface area will stay the same
If d>2t the surface area will decrease

The change in weight will be 3,1415 * <number of holes>^2 * t / 4 * <material density>.